1. Field of the Invention
The present invention relates to a function maintaining method for a fuel cell system used, for example, in a fuel cell vehicle.
2. Description of the Related Art
In a fuel cell mounted in a fuel cell vehicle, for example, an anode and a cathode that sandwich a solid polymer electrolyte membrane are provided, where the anode is supplied with a fuel gas (for example, hydrogen gas) and the cathode is supplied with an oxidant (for example, oxygen or air), and the electrochemical energy produced by the oxidization-reduction reaction of these gases is extracted as direct electrical energy.
As a fuel cell system that uses this type of fuel cell, there is a fuel cell system provided with a plurality of storage tanks (fuel tanks), and opening and closing valves are provided at respective flow inlets. A pressure sensor is installed along the flow path connected to the opening and closing valves, and by switching storage tanks depending on the pressure detected at the pressure sensor, the supply of hydrogen is carried out continuously (refer to Citation 1: Japanese Unexamined Patent Application, First Publication, No. 2001-295996).
However, when the pressure sensor fails, it is not possible to monitor the pressure of the fuel tank, and thus when generation of electricity continues as is, there is the concern that all of the fuel in the fuel tank will be consumed, and thus there is the problem that the function and reliability of the fuel cell system cannot be maintained, which is not desirable.
In consideration of the problem described above, it is an object of the present invention to provide a fuel cell system that can estimate the pressure of the fuel tank and can maintain the function and reliability of the fuel cell system even when the pressure sensor for the fuel tank has failed.
In order to attain the above object, according to the present invention, there is provided a function maintaining method for a fuel cell system, the fuel cell system including a fuel cell that is supplied fuel and an oxidant to generate electricity, a fuel tank that supplies the fuel to the fuel cell, a tank pressure sensor that detects a pressure of the fuel tank, comprising the steps of calculating, when a failure of the tank pressure sensor has been detected, the pressure of the tank before a predetermined time interval from the time of this detection and a fuel consumption amount and fuel discharge amount after the detection of the failure, and estimating the pressure of the tank according to the fuel consumption amount and the fuel discharge amount.
According to this invention, even in the case that a failure of the tank pressure sensor has been detected, the tank pressure of the fuel tank can be estimated by using the fuel consumption amount and the fuel discharge amount, and it is possible to estimate the remaining amount of fuel in the fuel tank thereby. Thus, it is possible to carry out control of the fuel cell depending on this estimated tank pressure, and at the same time, an operation that maintains the function of the fuel cell system becomes possible, and the function and reliability of the fuel cell system can be increased.
Preferably, the function maintaining method for a fuel cell system further comprises the step of stopping generation of electricity of the fuel cell when the estimated pressure of the tank becomes equal to or less than a predetermined value.
According to this invention, it is possible to operate the fuel cell in a state that reliably maintains fuel in the fuel tank at or above a constant amount, and thus the reliability of the fuel cell system can be increased.
Preferably, the fuel cell system further comprises a discharge valve that controls a fuel discharge amount of the fuel cell, and the fuel discharge amount is governed according to presence or absence of fuel discharge processing that opens the discharge valve.
According to this invention, by governing the fuel discharge amount depending on the presence or absence of fuel discharge processing, it is possible to estimate the pressure of the fuel tank with a higher precision, and thus a more precise control of the fuel cell becomes possible, and thereby the function and reliability of the fuel cell system can be improved.
Preferably, the fuel cell system further comprises a temperature sensor that detects a temperature of the fuel cell, and the fuel consumption amount and the fuel discharge amount are governed based on the temperature detected by the temperature sensor.
According to this invention, by governing the fuel consumption amount and the fuel discharge amount according to the temperature, it is possible to estimate the pressure of the fuel tank with a higher precision, and thus more precise control of the fuel cell becomes possible, and the function and reliability of the fuel cell system can be increased.
The above and other objects and features of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings.